A conventional optical modulator includes a package accommodating a substrate for optical modulation including an optical waveguide and plural signal electrodes interacting with the optical waveguide; and a wiring substrate including wires connected to the signal terminals. Among such optical modulators is an optical modulator that has wiring with numerous turns on the wiring substrate such that the electrical length of the wires differ from one another, whereby the optical modulator adjusts the phase differences among high-frequency electrical signals input into the signal electrodes (see, e.g., Domestic Republication of PCT International Publication for Patent Application, Publication No. 2010/021193). Another optical modulator uses a flexible wiring board as a wiring substrate (see, e.g., Japanese Laid-Open Patent Publication No. 2011-138049).
However, in such conventional optical modulators, the wires are disposed to have numerous turns on the wiring substrate and therefore, the size of the wiring substrate increases. The wiring substrate is disposed inside the package and therefore, a problem arises in that the size of the package increases by an amount corresponding to the increase in the size of the wiring substrate.